Process for the preparation of vinylaromatic copolymer redispersion powders redispersible in water

Abstract

A process for the preparation of vinylaromatic copolymer redispersion powders redispersible in water is by free-radical emulsion polymerization of a comonomer mixture including (a) one or more vinylaromatic comonomers, (b) one or more 1,3-diene comonomers (b1) or one or more comonomers (b2) from the group including the alkyl esters having 1 to 8 C atoms of acrylic acid or methacrylic acid and (c) 0.1 to 10% by weight, based on the total weight of the comonomer mixture, of one or more comonomers from the group including the ethylenically unsaturated mono- or dicarboxylic acids or the anhydrides thereof, the ethylenically unsaturated carboxamides, the ethylenically unsaturated sulfonic acid compounds and in each case the salts thereof, and drying of the aqueous copolymer dispersion obtainable thereby. One or more hydroxycarboxylic acids or the salts thereof are added to the aqueous copolymer dispersion in an amount of 3 to 40% by weight, based on the total weight of copolymer, before or during the polymerization or before the drying.

What is claimed is:  
     
       1. A process for the preparation of a vinylaromatic copolymer redispersion powder redispersible in water comprising the steps of free-radical emulsion polymerizing of a comonomer mixture comprising 
       (a) at least one vinylaromatic comonomer;  
       (b) at least one comonomer selected from the group consisting of a 1,3-diene comonomer (b1) and an ester comonomer (b2) selected from -the group consisting of an alkyl ester having 1 to 8 C atoms of acrylic acid and an alkyl ester having 1 to 8 C atoms of methacrylic acid and  
       (c) 0.1 to 10% by weight, based on the total weight of the comonomer mixture, of at least one ethylenically unsaturated comonomer selected from the group consisting of an ethylenically unsaturated monocarboxylic acid, an ethylenically unsaturated dicarboxylic acid and anhydrides thereof, an ethylenically unsaturated carboxamide, an ethylenically unsaturated sulfonic acid, and salts thereof; and  
       drying an aqueous copolymer dispersion obtained thereby; and  
       adding at least one hydroxycarboxylic acid or a salt thereof to the aqueous copolymer dispersion in an amount of 3% to 40% by weight, based on the total weight of copolymer, in a manner selected from the group consisting of before the polymerizing, during the polymerizing, and after the polymerizing but before the drying.  
     
     
       2. The process as claimed in  claim 1 , comprising 
       copolymerizing 15.0% to 85.0% by weight of vinylaromatic (a) and 15.0% to 85.0% by weight of 1,3-diene (b1) or (meth)acrylate (b2).  
     
     
       3. The process as claimed in  claim 1 , 
       wherein said vinylaromatic comonomer (a) is styrene.  
     
     
       4. The process as claimed in  claim 1 , 
       wherein said comonomer (b1) is 1,3-butadiene, and  
       wherein said ester comonomer (b2) is selected from the group consisting of methyl methacrylate, methyl acrylate, n-butyl methacrylate, n-butyl acrylate, ethyl methacrylate, ethyl acrylate, 2-ethylhexyl methacrylate and 2-ethylhexyl acrylate.  
     
     
       5. The process as claimed in  claim 1 , 
       wherein said comonomer (c) is selected from the group consisting of acrylic acid, methacrylic acid, fumaric acid, itaconic acid, crotonic acid, maleic acid, mesaconic acid, glutaric acid, maleic anhydride, acrylamide, methacrylamide, vinylsulfonic acid and 2-acrylamidopropanesulfonic acid.  
     
     
       6. The process as claimed in  claim 1 , 
       wherein said hydroxy carboxylic acid is selected from the group consisting of a monohydroxy carboxylic acid and a dihydroxy carboxylic acid of an acid selected from the group consisting of a monocarboxylic acid having 2 to 10 C atoms, dicarboxylic acid having 2 to 10 C atoms, tricarboxylic acid having 2 to 10 C atoms, a sodium salt thereof, a potassium salt thereof, an ammonium salt thereof and a calcium salt thereof.  
     
     
       7. The process as claimed in  claim 6 , 
       wherein said hydroxycarboxylic acid is selected from the group consisting of mandelic acid (hydroxyphenylacetic acid), lactic acid (2-hydroxypropionic acid), malic acid (hydroxysuccinic acid), tartaric acid (2,3-dihydroxybutanedioic acid) and citric acid (2-hydroxy-1,2,3-propanetricarboxylic acid).  
     
     
       8. The process as claimed in  claim 1 , 
       wherein the amount of hydroxycarboxylic acid is 7% to 30% by weight, based on the total weight of the copolymer.  
     
     
       9. A chemical product composition comprising 
       a substance selected from the group consisting of an inorganic hydraulically setting binder, a cement, a plaster, a water glass, a construction adhesive, a render, a filling compound, a floor filling compound, a concrete repair mortar, a joint mortar and a paint, in combination with  
       a redispersion powder redispersible in water produced by the process as claimed in  claim 1 .  
     
     
       10. A sole binder for coating materials and adhesives comprising 
       a redispersion powder redispersible in water produced by the process as claimed in  claim 1 .  
     
     
       11. A coating material and binder for textiles and paper comprising 
       a redispersion powder redispersible in water produced by the process as claimed in  claim 1 .  
     
     
       12. The process as claimed in  claim 1 , wherein the hydroxycarboxylic acid is added before the polymerizing. 
     
     
       13. The process as claimed in  claim 1 , wherein the hydroxycarboxylic acid is added during the polymerizing. 
     
     
       14. The process as claimed in  claim 1 , wherein the hydroxycarboxylic acid is added after the polymerizing but before the drying. 
     
     
       15. A process for the preparation of a vinylaromatic copolymer redispersion powder redispersible in water comprising the steps of 
       free-radical emulsion polymerizing of a comonomer mixture comprising  
       (a) at least one vinylaromatic comonomer;  
       (b) at least one comonomer selected from the group consisting of a 1,3-diene comonomer (b1) and an ester comonomer (b2) selected from the group consisting of an alkyl ester having 1 to 8 C atoms of acrylic acid and an alkyl ester having 1 to 8 C atoms of methacrylic acid and  
       (c) 0.1 to 10% by weight, based on the total weight of the comonomer mixture, of at least one ethylenically unsaturated comonomer selected from the group consisting of an ethylenically unsaturated monocarboxylic acid, an ethylenically unsaturated dicarboxylic acid and anhydrides thereof, an ethylenically unsaturated carboxamide, an ethylenically unsaturated sulfonic acid, and salts thereof; and  
       drying an aqueous copolymer dispersion obtained thereby; and  
       adding at least one hydroxycarboxylic acid or a salt thereof to the aqueous copolymer dispersion in an amount of 3% to 40% by weight, based on the total weight of copolymer, in a manner selected from the group consisting of before the polymerizing, and during the polymerizing.